This invention relates to devices for handling and transporting substantially identical objects in series, and more particularly to conveyors for delivering food items or other products at controlled intervals for automatic packaging.
Endless conveyors, particularly in the form of chains, are frequently employed to move a wide variety of solid materials. For example, a chain scraper conveyor for transporting granular and abrasive material is disclosed in U.S. Pat. No. 4,815,586 (Heising). More particularly, a pair of parallel chains carries spaced apart drivers through a trough to carry particulates through the trough. Rollers in the trough support the drivers and reduce friction.
U.S. Pat. No. 4,353,276 (Ackerfeldt) discloses an infeeding conveyor for work pieces to be cut by a stationary sawing machine. The conveyor includes two independently driveable endless chains, with at least one dogging means mounted to each chain. As one of the chains and dogging means feeds a log toward the saw, another one of the chains can be moved to align its dogging means for receiving the next log to be cut.
In many applications it is desirable to provide controlled, consistent spacing between adjacent drivers or pushers, to accommodate a series of substantially equally sized objects. In this regard, the most direct approach is to permanently secure the drivers, equally spaced apart from one another a distance slightly greater than the length of the objects to be conveyed. A device capable of limited adjustment of this spacing is disclosed in U.S. Pat. No. 3,198,316 (Bivans). A pair of endless chains, one carrying spaced apart leading fingers and the other carrying spaced apart lagging fingers, interact with sprocket for tilting the lagging finger backward to increase the size of the space for receiving the box, affording greater tolerance for a device that feeds the boxes to the conveyor.
With automatic packaging or wrapping of products, the need arises to feed items at controlled intervals for wrapping, and preferably at high speed. Horizontal wrapping machines, for example as disclosed in U.S. Pat. No. 4,506,488 (Matt et al), typically involve drawing and shaping a continuous film of pliable packaging material into a continuous tube that receives a series of spaced apart food items or other products to be packaged. The tube is drawn past sealing and cutting stations to individually package the products.
The introduction of computer controlled and servo motor operated drawing, sealing, cutting, etc. in wrapping devices affords the ability to pre-program product changeovers, which is a considerable advantage. However, a changeover to a product of different size traditionally has required a corresponding adjustment to the infeed conveyor to the wrapping device. Usually, this involves replacing one chain or endless conveyor with another conveyor having the appropriate spacing between pushers. Thus the changeover is time consuming and costly since the packing device can not operate during the changeover.
Therefore, it is an object of the present invention to provide an endless conveyor carrying multiple drivers along its length, in which selective subsets of the drivers can be actuated for controllably varying the distance between adjacent actuated drivers.
Another object is to provide a chain conveyor in which drivers carried by an endless chain are actuated by a means traveling approximately the same speed as the chain.
A further object of the invention is to provide, in connection with an endless chain carrying multiple actuatable drivers, a means for positively actuating or positively retracting each driver as it approaches a path for conveying objects.
Yet another object is to provide an endless chain drive with multiple drivers configured to avoid off-center loading of the drivers, and with guide means for substantially preventing movement of the endless chain normal to the direction of chain travel.